I'm assuming you are a supporter of Objectivism or Liberatarianism... If that's so, then you could find out what kind of financial rewards exist for translating books by your favorite authors into other languages. If someone who is a liberal at heart worked for a publisher who paid them to translate one of Ayn Rand's works into another language, I shudder to think of what some of sense-of-life subtelties came out like.
There are also books whose copyright has expired, mostly classics, and it might be that you could translate them into other languages and publish them (holding some sort of copyright, I believe). They could be published digitally.
And there are many authors that are currently publishing digitally to Amazon's Kindle and would probably provide a generous split of royalties for translations to other languages. This is a good time since it is a fairly new market, one that is growing, and other nations lag behind the U.S. I think Amazon makes public the sales numbers of all books - certainly a nice statistic to guide in which of the books you like might also generate nice royalties in other countries.
(These ideas are just off the top of my head and may have good reasons why they wouldn't work.)
Another concern is that linguistics is useless. Or that I'll have all these language skills and nothing interesting to say.
Being concerned about not having anything interesting to say is the wrong approach. You shouldn’t speak or write to be of interest to others, but to enjoy the productive process of the writing or speaking. And if you are still young (twenties?) I'd put more time in becoming the kind of person, in terms of character and basic skills, than working about stepping into just the right job.
Only a tiny portion of the population have some kind of passionate career drive that they are clear about early in life. Most of us have to find those areas where we feel really good about the particular productive activities we engage in. In that case it often involves some experimentation.
Just thought I’d mention this: Leonard Peikoff has a recorded course titled “Philosophy of Grammar” and in its new digital, downloadable audio format, it is very convenient and I highly recommend it. For you this might be a fascinating step away from the usual linguistics courses – away from the anthropology/phonetics/semantics/semiotics or typical Linguistic Analysis philosophical nonsense to an objective philosophical side of language as a logically functional representation of thought. I mention this because things are on sale at the Ayn Rand Store for about a week, and because I have the CD version they made this from and can recommend it highly. It’s available for $17.50 and when the download is unzipped it is over 19 hours of recorded lecture.